Modern electronic devices, such as transistors, often generate considerable heat. If provisions are not made to cool the device, the device can exceed its operating temperature and fail. In addition, adequate cooling of a device can lengthen its service life and increase reliability.
A common technique for cooling an electrical device is the use of a heat sink. The electronic device is mounted on the heat sink so that the heat generated in the device is readily transferred to the heat sink. The heat sink has a configuration, including cooling fins, which provides effective dissipation of heat from the heat sink to the atmosphere, either by natural convection or forced convection by use of a cooling fan.
Electronic devices are typically employed within a circuit laid out on a circuit board. If the electronic device is mounted on a heat sink, the heat sink will, in turn, be mounted to the circuit board with the necessary electrical connections being made between the device and the circuit board.
In the past, solid roll pins have been employed to mount a heat sink on a circuit board. The heat sink will be formed with an aperture of diameter equal to or slightly less than the diameter of the roll pin for an interference fit between the roll pin and the heat sink. A hole will be formed on the circuit board which also has a diameter equal to or less than the diameter of the roll pin so that the roll pin will also have an interference fit with the circuit board. Unfortunately, the use of such a solid roll pin requires extremely fine tolerances in the heat sink and circuit board which are often difficult and expensive to achieve. Furthermore, if either the hole in the circuit board or aperture in the heat sink are enlarged through wear, the heat sink will no longer be securely mounted to the circuit board.
The CEM Company has introduced a roll pin marketed under the trademark "Spirol". This pin is formed by rolling a sheet of material into a tight helix, thereby resembling a cylinder. The helix can extend two complete revolutions about its center axis. While this has been an improvement on the conventional solid roll pin, the "Spirol" roll pin will frequently be too large in diameter or too small in diameter, which either makes it difficult to mount the heat sink on the circuit board or prevents the heat sink from being securely mounted thereon.
In addition to simply mounting the heat sink on a circuit board, it is often desirable to space the heat sink from the board to permit free airflow past the bottom of the heat sink. With the conventional roll pins noted above, it is very difficult to position the heat sink at a precise distance from the circuit board using the pins alone.
A need therefore exists for a roll pin having an enhanced ability to secure a heat sink to a circuit board with less emphasis on precise control of the diameter of the hole in the circuit board and the aperture in the heat sink. Furthermore, a need exists for a roll pin which permits precise positioning of the heat sink at a spaced distance from the circuit board.